Proper drainage is an important consideration in the design and construction of subterranean foundations. In the absence of proper drainage, water can penetrate into the structures through tiny cracks or other openings, causing severe damage or leakage.
The problem of proper drainage has historically been addressed by guiding water away from the structure through a "French drain," a perforated horizontal drain pipe that extends along the bottom of the foundation. The perforated drain pipe is surrounded by gravel to prevent it from being crushed by the surrounding soil and to prevent soil from entering the drain pipe through the openings. Water from the soil seeps into the drain pipe, and is carried away.
As described in U.S. Pat. No. 4,840,515 to James S. Freese, thin drainage panels can be also be used in conjunction with French drains to help collect water in the vicinity of the foundation. Each drainage panel includes a sheet-like base and a filter media separated from the base by a plurality of dimples or projections that extend from the base. The resulting structure is a thin panel with a hollow interior between the base and the filter media. The panel is placed against the outside wall of a foundation, with the filter media facing outwards, and with the bottom of the panel terminating at a French drain. Soil is then back-filled against the foundation and panel, sandwiching the panel between the soil and the vertical foundation wall. Water from the soil penetrates into the panel through the water-permeable filter material, and trickles downward through the panel and into the French drain.
While drainage panels such as those disclosed in the Freese patent have proven useful, they can still be further improved. Most notably, drainage panels in the prior art are designed primarily to protect the vertical wall of the foundation, without providing adequate protection for the horizontal surface of the foundation's footing and without protecting the cold joint that exists where the vertical foundation wall meets the horizontal foundation footing. As a result, water can impregnate the cold joint, causing damage to the foundation. To the extent prior art panels can be used to cover both the vertical foundation wall and the horizontal foundation footing, they are difficult to bend to conform to the intersection of the foundation and the footing, where the foundation meets the footing usually at a 90 degree angle.
In addition, prior art drainage panels are typically used in conjunction with, rather than in place of, a French drain system. This requires that the lower edge of the drainage panel be connected into a French drain system along the entire length of the foundation wall, complicating the installation and increasing costs.
In view of these disadvantages with prior art drainage systems, it is an object of the present invention to provide a subterranean drainage system that does away with the need for a common French drain system, without the need for any gravel or perforated pipe. A further object of the present invention is to provide a subterranean drainage system that can be easily installed to protect and conform closely to both the vertical outer surface of a foundation wall and the horizontal upper surface of the foundation footing, while protecting the cold joint between the foundation and the footing. Finally, it is a further object of the invention to provide a drainage system in which the panel provides efficient drainage of water along the entire length of a foundation wall, and can be readily connected into a standard drain pipe at any desired point to drain water away from the panel and the foundation.